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Order blinded paths by reliability criteria #2912

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Merged
merged 2 commits into from
Mar 7, 2024
Merged

Order blinded paths by reliability criteria #2912

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5e9a998
Prefer well-connected nodes for introduction nodes
jkczyz Feb 28, 2024
e105833
Prefer one-hop blinded path to Tor intro nodes
jkczyz Feb 28, 2024
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50 changes: 50 additions & 0 deletions lightning/src/ln/offers_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -263,6 +263,56 @@ fn prefers_non_tor_nodes_in_blinded_paths() {
}
}

/// Checks that blinded paths prefer an introduction node that is the most connected.
#[test]
fn prefers_more_connected_nodes_in_blinded_paths() {
let mut accept_forward_cfg = test_default_channel_config();
accept_forward_cfg.accept_forwards_to_priv_channels = true;

let mut features = channelmanager::provided_init_features(&accept_forward_cfg);
features.set_onion_messages_optional();
features.set_route_blinding_optional();

let chanmon_cfgs = create_chanmon_cfgs(6);
let node_cfgs = create_node_cfgs(6, &chanmon_cfgs);

*node_cfgs[1].override_init_features.borrow_mut() = Some(features);

let node_chanmgrs = create_node_chanmgrs(
6, &node_cfgs, &[None, Some(accept_forward_cfg), None, None, None, None]
);
let nodes = create_network(6, &node_cfgs, &node_chanmgrs);

create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 1_000_000_000);
create_unannounced_chan_between_nodes_with_value(&nodes, 2, 3, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 1, 4, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 1, 5, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 2, 4, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 2, 5, 10_000_000, 1_000_000_000);

// Add extra channels so that more than one of Bob's peers have MIN_PEER_CHANNELS and one has
// more than the others.
create_announced_chan_between_nodes_with_value(&nodes, 0, 4, 10_000_000, 1_000_000_000);
create_announced_chan_between_nodes_with_value(&nodes, 3, 4, 10_000_000, 1_000_000_000);

let (alice, bob, charlie, david) = (&nodes[0], &nodes[1], &nodes[2], &nodes[3]);
let bob_id = bob.node.get_our_node_id();

disconnect_peers(alice, &[charlie, david, &nodes[4], &nodes[5]]);
disconnect_peers(david, &[bob, &nodes[4], &nodes[5]]);

let offer = bob.node
.create_offer_builder("coffee".to_string()).unwrap()
.amount_msats(10_000_000)
.build().unwrap();
assert_ne!(offer.signing_pubkey(), bob_id);
assert!(!offer.paths().is_empty());
for path in offer.paths() {
assert_eq!(path.introduction_node_id, nodes[4].node.get_our_node_id());
}
}

/// Checks that an offer can be paid through blinded paths and that ephemeral pubkeys are used
/// rather than exposing a node's pubkey.
#[test]
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10 changes: 7 additions & 3 deletions lightning/src/onion_message/messenger.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -364,13 +364,17 @@ where
network_graph
.node(&NodeId::from_pubkey(pubkey))
.filter(|info| info.channels.len() >= MIN_PEER_CHANNELS)
.map(|info| (*pubkey, info.is_tor_only()))
.map(|info| (*pubkey, info.is_tor_only(), info.channels.len()))
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I think choosing the right introduction points in order to optimize for a specific metric such as reliability is very related to finding optimal autopilot/attachment strategies. Using the node degree as a proxy metric for reliability seems like a solid first step, especially if we're talking about payment reliability.

A few more thoughts though: Further down the road we could also entertain a few other metrics that could make sense, for example optimizing for betweenness centrality or choosing introduction points according to k-Center optimization. (Some of our simulation results in this paper might be of interest here, see for example Fig. 1). Also, we could account for node uptime (regularity of node announcements?) or latency metrics, that might become available as part of the attributable errors proposal?

Doing anything more than just scoring by node degree might of course require us to pre-calculate and store more per-node metrics, so would probably only make sense if we'd ever come around to introduce a node score, possibly as part of #63?

)
.collect::<Vec<_>>();
peer_info.sort_unstable_by(|(_, a_tor_only), (_, b_tor_only)| a_tor_only.cmp(b_tor_only));

// Prefer using non-Tor nodes with the most channels as the introduction node.
peer_info.sort_unstable_by(|(_, a_tor_only, a_channels), (_, b_tor_only, b_channels)| {
a_tor_only.cmp(b_tor_only).then(a_channels.cmp(b_channels).reverse())
});

let paths = peer_info.into_iter()
.map(|(pubkey, _)| vec![pubkey, recipient])
.map(|(pubkey, _, _)| vec![pubkey, recipient])
.map(|node_pks| BlindedPath::new_for_message(&node_pks, &*self.entropy_source, secp_ctx))
.take(MAX_PATHS)
.collect::<Result<Vec<_>, _>>();
Expand Down